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In the transmission process of gear transmission system of three-cylinder engine, there are great vibration and noise problems. Therefore, a rigid-flexible coupling model of gear transmission system with damping ring was proposed, and the motion characteristics and vibration suppression performance of flexible gear structure were studied experimentally. Firstly, a 6-degree-of-freedom bending and torsional model of the gear transmission system with additional damping ring was established by using the lumped mass method. Ishikawa formula was used to calculate the time-varying meshing stiffness of the flexible gear. The vibration response of the gear system with and without damping ring was compared. Then a special gear transmission system test equipment was built to test the acceleration and noise peak of steel gear and flexible gear at different speeds. Finally, a laser displacement test bench was designed to compare and analyze the micro-jitter of the gears under different rotational speeds, and the vibration reduction effect of the flexible gears was verified, and the theoretical model was verified. The esearch results show that the maximum acceleration signals of steel gear and flexible gear are respectively 35. 58 m/ s 2 and 20. 37 m/ s 2, when the speed is 1 000 r/ min. When the gear speed is 4 000 r/ min, the damping effect of the flexible gear is the best, the peak acceleration is reduced by 45. 23%, and the peak noise is reduced by 39. 06% . The micro-jitter amplitude of steel gear is obviously higher than that of flexible gear, and the change trend of both is similar. The flexible gear can effectively suppress the unsmooth and burr phenomenon of the micro-jitter amplitude curve of the gear teeth, thus enhancing the stability of the balance shafting of the three-cylinder engine. [ABSTRACT FROM AUTHOR]

In order to systematically study the influence of valve body structural parameters on the flow resistance characteristics of the regulating valve, the model of the regulating valve body in power station was established by using the numerical simulation method. Combined with the orthogonal experimental design, the influence of different structural parameters of the regulating valve body on the convection resistance characteristics was studied. The results show that the influence degree of the structural parameters of the regulating valve body on the convection resistance coefficient is in the order of upper chamber radius > lower chamber height > upper chamber height > valve body half-length > lower chamber radius > middle chamber radius. Meanwhile, the optimization analysis of the inlet angle of the valve body shows that the smaller the inlet angle is, the smaller the flow resistance coefficient is. The optimal structure obtained after orthogonal experiment optimization and inlet angle optimization, its flow resistance coefficient is reduced by 19. 45% compared with the original structure, and the flow characteristic curve is more ideal. The research results can provide theoretical support for the structure optimization of sleeve type regulator valve. [ABSTRACT FROM AUTHOR]

The complex coupling nonlinearity, model uncertainty, and external load uncertainty of the electro-hydraulic servo system of medium and large excavators resulted in large trajectory tracking errors and poor dynamic performance of the system. A backstepping controller based on interconnection and damping assignment ( IDA) framework was proposed to improve the tracking performance and robustness of excavator working devices in mining tasks. Firstly, a state space model of the electro-hydraulic servo system was constructed using pilot valve, valve controlled asymmetric cylinder, and valve controlled asymmetric cylinder models. Furthermore, based on Hamiltonian theory, the state space model was constructed as a third order open-loop port Hamiltonian ( pH) system with disturbances. Based on the interconnection matrix and damping matrix structure obtained from the pH system, the virtual control signal was gradually designed and the control law was ultimately obtained. Then, a matching equation was constructed to simplify the design and calculation process on other systems, and the expected energy function was used as a candidate Lyapunov function. Based on the Lyapunov stability theorem, the convergence and stability of the closed-loop system at the expected trajectory were proved. Finally, the trajectory tracking performance of the proposed control algorithm was verified through numerical simulation experiments on the excavator bucket and its electrohydraulic servo system. The research results show that, without considering model uncertainty, the proposed controller improves convergence speed in position control by 1. 9% to 6. 3% compared to the other three controllers; maintaining excellent convergence speed in trajectory tracking while reducing maximum tracking error by 70% to 81% . In the case of model uncertainty and time-varying loads, the maximum tracking error in the face of impact only increases by 0. 004 m, and the required control input for adjustment is reduced by 4% to 20% . The above results indicate that the proposed control algorithm has better comprehensive tracking performance and robustness. [ABSTRACT FROM AUTHOR]

【Objective】 To study the effects of foliar spraying phosphorus, potassium and boron fertilizers on broad bean yield, and provide a basis for the application of foliar fertilizers in broad bean production. 【Methods】 LX-17 broad bean was used as test material. 4 treatments, boron (B), potassium dihydrogen phosphate (PK), boron and potassium dihydrogen phosphate combined application (PKB) and no fertilizer (CK) were applied to broad bean once at budding stage, initial flowering stage and final flowering stage. The agronomic traits, fresh bean yield, dry bean yield, and seed quality of broad bean under each treatment condition were determined. The correlation analysis between each trait and the yield of fresh and dry beans was carried out. 【Results】 Both PK and PKB treatments increased broad bean stem thickness while lowering plant height and internode length. B treatment decreased the plant height and stem thickness when high concentration boron fertilizer was used, which was significantly different from CK (P<0.05) . All three foliar spraying treatments increased the effective branch number. PKB treatment increased the number of fresh and dry pods per branch of broad bean, decreased the dry weight of 100 seeds, and was significantly different compared with CK (P<0.05) . The number of fresh and dry pods per branch of broad bean decreased as the concentration increased in the B treatment, whereas the number of seeds per pod increased. B0.10 treatment had the best result. Correlation analysis of the yield and other indicators showed that yield was significantly or extremely significantly positive correlated with stem diameter, number of seeds per pod, number of fresh pods per branch, and fresh weight of 100 seeds. Compared with CK, PK and PKB treatments had no significant effect on the germination rate and germination potential of broad bean seeds (P>0.05) . PK treatment increased the first grade rate of broad bean seeds. High concentration of B treatment decreased the germination rate, potential germination rate and first-class rate. 【Conclusion】 Spraying potassium dihydrogen phosphate, low-concentration boron fertilizer, and foliar fertilizer combined with potassium dihydrogen phosphate and boron fertilizer during the budding stage, initial flowering stage and final flowering stage could promote the broad bean growth and increase the yield. The combined application of 0.3%-0.4% potassium dihydrogen phosphate and 0.1% boron had the best treatment effect. [ABSTRACT FROM AUTHOR]

To improve the accuracy of the optimization parameters of the cyclone and obtain the optimal solution in structure optimization, a new type of composite hydrocyclone was taken as the research object, the single factor analysis optimization method based on correlation analysis was used to guide the selection of optimization range and improve the accuracy of optimization range of structural parameters. Based on the response surface optimization method, the optimal structural parameters of the hydrocyclone were determined with the separation efficiency as the optimization objective, and the regression model between the separation efficiency and the structural parameters was obtained. The results show that the significant relationship between different structural parameters and each performance index is not the same. According to the results of correlation analysis, the optimal range of each structure is as follows. The upper cone angle is 0° ~ 4°, the lower cone angle is 8° ~ 12°, and the diameter of the bottom nozzle is 12 ~ 16 mm. The optimal structure of the cyclone obtained by response surface optimization is as follows: the upper cone angle is 2. 565°, the lower cone angle is 11. 719°, and the diameter of the bottom flow port is 12. 889 mm. Under these parameters, the solid separation efficiency of the hydrocyclone reaches 99. 945%, and the gas separation efficiency reaches 93. 807% . It provides a new method to optimize the structure of hydrocyclones. [ABSTRACT FROM AUTHOR]

In some cases, moment of inertia of an object is needed for investigating its rotation characteristics. For most objects with uniform distribution mass and regular shape, the moment of inertia can be calculated by theoretical method. While for most uneven mass or irregular shaped object, the experiment method of measuring the moment of inertia becomes the only adoption. In this paper, the commonly used methods to determine the moment of inertia are introduced and compared, and the disvantages and defects of various kinds of measurement method are discussed. Then, as an example, the method of determination of drop hammer test is adopted to measure the moment of inertia relative to the rotational axis of powder metallurgy technology molding pulley, and the experimental error together with the causes are analysed. Finally, the problems and solving skills during the measuring process of moment of inertia are introduced for serving as a reference for technical personnel. [ABSTRACT FROM AUTHOR]

Objective To explore the role of functional skincare products in improving sensitive skin. Methods A total of 60 subjects with sensitive skin were selected by lactic acid sting test and randomly divided into the treated and control groups, 30 subjects per group. The treated group used tone repair skincare product and the untreated group served as the controls. The improvements in skin hydration, transepidermal water loss, a* value, redness area, and investigators' and subjects' self-evaluation scores were compared between the two groups 2 hours and 28 days after the applications. Results Compared to the control group, 28-day applications of tone repair skincare product significantly improved lactic acid sting scores(Z=-2.83, P<0.05). The stratum corneum hydration levels were increased both 2 hours and 28 days after topical applications of the products. In contrast, transepidermal water loss rates were dramatically decreased after 28-day applications (P<0.05, vs. controls). Both a* value and proportion of redness area were markedly decreased 2 hours after application of the product (P<0.05 for both). However, no significant differences in a* value and proportion of redness area were observed between the treated and control groups after 28-day applications. The investigators' assessment showed significant improvements in sensitive skin symptoms and sign, such as dryness, scales, telangiectasia and skin tightness in the treatment group compared to the control group (P<0.05). Conclusions Functional skincare products can improve the skin barrier function, playing an important role in improving the physiological state of sensitive skin. [ABSTRACT FROM AUTHOR]

The generation of power shift tractor promotes the automatic driving of agricultural machinery to the direction of unmanned, and the automatic obstacle avoidance of agricultural machinery has become a key issue to be solved. Most of the existing obstacle avoidance path planning adopts the shortest tangent method, which has the advantages of fast and simple path generation and short track, but the curvature of the path curve is discontinuous and there are corner inflection points, which make the tractor front wheel angle suddenly change and affect the obstacle avoidance accuracy. In this paper, for the curvature discontinuity of the shortest tangent path curve, poor tracking control accuracy and low precision of agricultural machinery model, the third-order bezier curve optimization method was used to form a continuous smooth agricultural machine obstacle avoidance path. The optimized curve curvature was continuous and the obstacle avoidance path was smooth with no turning points, which was conducive to the control of agricultural machinery driving. The linear control model of agricultural machinery movement was established by chain control theory, and the PI controller was used for corner compensation to improve the accuracy of agricultural machinery obstacle avoidance. The simulation of the path tracking control method was completed. The simulation results showed that the heading error angle of the agricultural machinery was mostly in the range of - 0.06-0.06 rad, the lateral position error was less than 13 cm, and the front wheel steering angle changed gently with no significant mutation, indicating that the control method of the obstacle avoidance path control method had a high precision, and the agricultural machinery can drive according to the preset trajectory. The ploughing operation test was carried out, and the Dongfanghong LF954-C power shift tractor was used, which can automatically start, stop, shift, and implement the lifting operation of the farm. The tractor was equipped with the Beidou agricultural autopilot with the straight running accuracy of ±2.5 cm. Ultrasonic radar and image recognition technology were used to perceive obstacles in the working environment. The farm implement was a 250 cm wide plow. A haystack obstacle was set on the machine working path with a contour radius smaller than the minimum turning radius of the tractor. The results of the plowing operation test showed that the machine can automatically complete the straight-line driving, farm implement lifting, automatic obstacle avoidance, farm implement falling, and continuous straight-line operation. The obstacle avoidance accuracy of the bezier curve was 5.21 cm, and the tracking control effect of the curve path was well. The accuracy of the agricultural machine continuing to travel in a straight line after obstacle avoidance was 1.98 cm, which indicated that the path tracking control method can ensure the tractor straight-line automatic driving after obstacle avoidance. The above results showed that the obstacle avoidance path and control method showed good robustness and adaptability in uneven ploughing land and can meet the obstacle avoidance requirements of tractor operation. [ABSTRACT FROM AUTHOR]